Managing fraud is U.S. online merchants' biggest concern about accepting global payments, according to a recent study by CyberSource Corp. Forty percent of internet retailers cited this, compared with 17 percent that said their biggest concern was implementing and managing connections with payment processors in foreign countries.

Doug Schwegman, director of customer and market intelligence for CyberSource, said he was surprised that managing fraud scored the highest among respondents. He had expected the top concern would be navigating legal and underwriting requirements of foreign markets. That ranked third, and was cited by 15 percent of respondents.

"Fraud should still be in the top three, but many merchants probably have not researched legal requirements," Schwegman says. "It is a big administrative problem and can slow you down, in terms of getting into a foreign market quickly."